Age/sex: 2½-year-old female
Size: 12.0 x 11.2 x 5.3 cm
The specimen shows a mildly thickened parietal pericardium (arrows) and a markedly dilated pericardial cavity (C). The brown appearance of the pericardial surface is due to degenerated blood. Although the cavity was reported to be filled with pus at the time of autopsy – thus implying acute infectious pericarditis – the smoothness of its surface is more suggestive of chronic disease.
Pericardium
The pericardium encases the heart and consists of two parts that surround a potential space (pericardial cavity). The inner portion (visceral pericardium) is attached to the outer surface of the heart muscle and consists of a very thin layer of connective tissue lined by mesothelial cells. The outer portion (parietal pericardium) is also lined by mesothelial cells but has a much thicker (1 -2 mm) fibrous base. The mesothelial cells produce fluid that acts as a lubricant for the heart to move easily within the cavity. Normally, this fluid measures about 20 - 30 ml and is constantly secreted and reabsorbed so that it does not accumulate and interfere with cardiac function.
Pericardial disease can affect the heart’s function in several ways. Rapid accumulation of pus in the cavity as a result of acute inflammation (acute pericarditis) can result in compression of the heart, impairing flow of blood from the atrium to the ventricle during diastole and thus outflow to the aorta during systole (cardiac tamponade). Bleeding from a ruptured myocardial infarct can have the same outcome. Fibrous thickening of the parietal pericardium (chronic pericarditis) can have a similar effect, although developing more slowly, and is sometimes termed constrictive pericarditis.
Below: Histology of chronic pericarditis (M - myocardium; I - inflammatory cells in pericardium.
Source: Rajaram A (2023). Chronic pericarditis.
